IEEE C802.16m-08/309
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Equal-Gain Precoder for Closed Loop MIMO Transmission
Date
Submitted
2008-05-05
Source(s)
Yu-Tao Hsieh, Chen-Ming Chen, ChienYu Kao, Chao-Wang Hwang, Pang-An
Ting, Richard Li
ITRI
Voice: +886-3-5914854
E-mail: ythsieh@itri.org.tw
Shang-Ho Tsai
NCTU
Re:
Call for Contributions of IEEE 802.16m_08/016r1 on the topic of DL MIMO schemes
Abstract
This contribution proposes a MIMO precoding scheme to improve the conventional precoding
approach with fewer feedback overhead.
Purpose
Discussion and approval by the task group.
Notice
Release
Patent
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Equal-Gain Precoder for Closed Loop MIMO Transmission
Yu-Tao Hsieh, Chen-Ming Chen, Chien-Yu Kao, Chao-Wang Hwang,
Pang-An Ting, Richard Li,
ITRI
Shang-Ho Tsai
NCTU
Introduction
In the IEEE 802.16m System Requirements [1], The MIMO technique with different antenna configurations is
regarded as one of the basic components for improving the system capacity without expanding the channel
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IEEE C802.16m-08/309
bandwidth. It is well known that the precoding/beamforming approach is widely used in WirelessMANOFDMA Reference System with designated precoding vector/matrix [2]. It is also demonstrated that the
existing precoding matrix in the Reference System features fixed amount of feedback overhead and searching
complexity due to constant codebook size. In this contribution we propose an equal-gain precoding matrix for
MIMO scenarios. We show in the following sections that the proposed precoding matrix will attain the similar
system performance with less feedback overhead.
Equal-Gain Precoding Matrix
In the existing closed loop precoding MIMO techniques a set of precoding vectors/matrices are adopted based
on the time-varying MIMO channel. The codebooks are designed independent of the number of transmit or
receive antennas. On the other hand, the proposed equal-gain precoding matrix quantizes the precoding matrix
using the equi-spaced constellations on the unit circle. The number of constellation points is formed by M=2q
where q denotes the bitwidth of the codebook as shown in Figure 1 as an example. Note that although the
consumed bit number for the precoding matrix may grow in the number of M by N where M is the number of
transmit antennas and N is the number of receive antennas, the proposed precoding matrix can attain the similar
system performance using a total of less feedback overhead than the existing precoding matrix.
-1
1
Figure 1 Example of an equal-gain precoder with bitwidth q=3
Simulations
The simulation evaluates the system performance of the existing precoding matrix and the proposed equal-gain
approach. We let M=4 and N=1. The feedback overhead of the existing precoding matrix is fixed at 6 bits per
precoding MIMO transmission.
Proposed Texts
We suggest the following proposed texts
============== Start of proposed texts =================================================
11.x Physical layer
11.x.y DL MIMO schemes
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IEEE C802.16m-08/309
11.x.y.z Precoding MIMO
In the precoding MIMO schemes, the equal-gain precoder with equi-spaced constellations can be taken
into consideration for improving the system performance while decreasing the feedback overhead.
Figure x shows an example.
-1
1
Figure x Example of equal-gain precoder with encoding bitwidth of 3.
============== End of proposed texts ================================================
References
[1] M. Cudak, “802.16m System Requirements,” IEEE 802.16m-07/002r4
[2] IEEE P802.16-2005, Section 8.4.5.4.10.15.
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